A petition launched in December by MySQL creator Michael 'Monty' Widenius to 'save' the open-source database from Oracle has quickly gained momentum, collecting nearly 17,000 signatures. Widenius on Monday submitted an initial batch of 14,174 signatures to the European Commission, which is conducting an antitrust review of Oracle's acquisition of Sun Microsystems, MySQL's current owner. The petition calls for authorities to block the merger unless Oracle agrees to one of three "solutions", including spinning off MySQL to a third party and releasing all past versions and subsequent editions for the next three years under the Apache 2.0 open-source license.

I used to hear this argument a lot back when MySQL had much less features than it does today, and it was wrong back then.
Most relational database systems are much more than simple data stores. And applications should care about how data is stored if they want efficient performance from a relational database.